For many years it has been common practice to apply a liquid to a surface using a brush, the brush first being dipped in a reservoir of the liquid and then wiped over the surface to be coated. For relatively large surface areas, rollers rather than brushes are used, the roller also being dipped in a reservoir of the liquid and then rolled across the surface to be coated. As an alternative to the use of a brush or roller, a pad has, in more recent times, sometimes been used: again, the pad is dipped in a reservoir of the liquid and then wiped across the surface to be coated.
The mode of application described above is unduly time consuming because of the necessity to dip the applicator (brush, roller or pad), in the liquid at frequent intervals in order to replenish the supply of liquid on the applicator. This is a particular problem when the user is standing on a ladder or a pair of steps which is frequently the case, for example when painting a ceiling. To mitigate this problem it has been proposed in the case of rollers to increase the liquid capacity of the roller by providing it with its own small liquid reservoir; this attempted solution, however, considerably increases the weight of the roller making it very tiring to use.
From time to time throughout this century it has been proposed to provide the liquid applicator with a connection via a length of tube to a reservoir of liquid and to feed the liquid from the reservoir to the applicator by pressure generated by a pump. This arrangement has the considerable advantage over the conventional arrangements described above that a user does not continually have to resplenish the liquid on the applicator nor does the applicator have to be excessively heavy. These proposed pressurised arrangements have not, however, proved satisfactory. If the reservoir of liquid and its associated pump is placed on the ground during application of the liquid then a long length of tubing is required between the reservoir and the applicator and this can impede the user. If, on the other hand, the reservoir and pump are carried by the use then this impedes the user during painting and is tiring as a result of the weight of the reservoir and pump assembly.
It is known to disperse a liquid from a container using a small capsule of pressurized gas. For example, soda syphons have been available for some years operating on this principle. National Can Corporation have disclosed a paint apparatus in which a container of paint is pressure fed by pressurized gas from a capsule to a roller; in operation the container is rested on the ground and a long length of tubing connected between the container and the roller to allow a user to paint a surface, holding the roller alone. An illustration of this proposed apparatus appeared on pages 30A and 31A of the Journal of Paint Technology Vol. 40, No. 521, June 1968. Liquid containers pressurized by capsules of gas are also described in U.S. Pat. Nos. 3,352,457 and 3,558,010 assigned to National Can Corporation.
The painting apparatus proposed by the aforesaid patents ('457 and '010) still suffers various drawbacks. The use of a long length of tubing can impede the user as already mentioned and also this apparatus, as well as the pressurized arrangements already described, is difficult to clean and messy to use. If the painting apparatus includes its own pressure vessel for containing the paint, the paint must first be poured into this vessel and then, after painting, any paint left in the vessel must be poured out and the vessel, in addition to all the rest of the apparatus, must be cleaned. The time saved during painting with the apparatus may thus be consumed in extra time spent preparing the apparatus for use and cleaning the apparatus after use.
To some extent, the cleaning operation can be reduced by supplying the paint in its own pressure vessel to which the pressurizing arrangement is then directly attached, since this avoids the need to clean the vessel after use. However, in this case the vessel containing the paint must be specially constructed both to withstand the pressure contained in the vessel during use and to receive the pressurizing arrangement. This greatly increases the cost of the paint vessel over a conventional paint can.